We believe therapeutic gain is enhanced when hyperthermia and radiation therapies are delivered simultaneously or within a very short time interval, and when these two modalities are focused efficiently into the target disease while minimizing dose to surrounding normal tissues. We further believe that a surface-conforming applicator can be constructed for effective combination of heat and High Dose Rate (HDR) brachytherapy of large area superficial disease over contoured anatomy. The long-term goal of this research is to fabricate clinically useful, operator and patient friendly conformal applicators for simultaneous heat and HDR brachytherapy of superficial tissue disease. To accomplish this goal, the proposed effort will combine the uniform heating capabilities of conformal microwave array (CMA) printed circuit board applicators, developed at UCSF, with improved patient interface that allows simultaneous positioning of HDR radiation sources for uniform brachytherapy dose distribution across the tissue surface. Our approach to realize this goal and to test the above hypothesis will require three specific aims: (1) Design and Construction of Combination Applicator (2) Study of Radiation Dosimetry (3) Evaluation of Combination Applicator Performance. The design of the applicator will integrate the CMA, water bolus and uniform arrays of catheters/channels for temperature monitoring probes and HDR brachytherapy sources. Emphasis will be on maintaining appropriate spacing of radiation sources for uniform dose distribution while allowing fast, reliable setup and ensuring intimate, comfortable contact with the skin surface. We will study radiation dosimetry to theoretically optimize bolus design, positioning of catheters, and materials selection. We will study perturbations of CMA components, and effect of variable bolus thickness on radiation dose uniformity. Evaluation of applicator performance will include measurement of power deposition pattern uniformity with E-Field scans in homogenous phantom, quantitative assessment of radiation dose uniformity with computer treatment planning and dosimetry measurements in homogeneous phantom tissue. We will verify that radiation does not adversely affect heating patterns or temperature monitoring accuracy and that heat applicator and temperature monitoring do not adversely affect radiation dosimetry.